As I recall, eons ago, there were some cross-arguments about the necessity for
arm and helmet straps, and I thought I
would add this to the discussion.
In mid-August, I found that a former girlfriend had rolled her SUV on the way
home from work last May. Her most
immediately life-threatening injuries were the result of a loose scuba tank
stored in the rear. As the car was rolling,
she got twisted in the seat so that the tank hit her on the right side of the
head (must have really been traveling,
because after it hit her, it went through the windshield and was found 200 ft.
from the car).
She's had lots of problems related to those injuries, but her most persistent
problems are related to her head thrashing
around as the car rolled. I've had to do a crash course in traumatic brain
injuries in the last couple of months and in
reading, and talking to her, her persistent problems (olfactory hallucinations
and a complete left-side visual field
cut) are related to the shearing that occurs when the head is thrown around
violently. Medically, shearing is described
principally as the skull being turned at a high rate, and the brain, being
softer and more massive than the skull,
inertially resists turning with the skull. The result is that the long nerves
(axons) of the brain are stretched and
torn. A secondary effect is that the outer surface of the cortex scrapes
against the bony ridges of the inside of the
skull, which destroys a lot of brain cells.
Shearing is the same phenomenon that produces the "punch-drunk" symptoms in
boxers who have taken too many right hooks
to the jaw.
I suppose if one is young and strong, with well-toned neck muscles, one can
resist some of the flailing, but for us
older folks, it makes sense to limit head travel with helmet straps--even a
fairly wide freedom-of-movement included
angle of 40 degrees significantly reduces the chance of shearing injuries.
As for arm straps, my friend has a very tough and painful inch-wide band of
scar tissue on her left triceps because, I
think, the window was open and her arm was caught between the door b-post and
the ground as the car rolled. Not enough
to break her arm, but enough to severely damage the muscles.
Of course, if one is sure that the shiny side will always be up and rubber side
will always be down, then I suppose none
of this applies.
Cheers.
--
Michael D. Porter
Roswell, NM
[mailto:mporter@zianet.com]
Never let anyone drive you crazy when you know it's within walking distance.
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